scholarly journals Self-assembly of spectrin oligomers in vitro: a basis for a dynamic cytoskeleton.

1981 ◽  
Vol 88 (2) ◽  
pp. 463-468 ◽  
Author(s):  
J S Morrow ◽  
V T Marchesi
Keyword(s):  
Self Assembly ◽  
Erythrocyte Membranes ◽  
Membrane Structure And Function ◽  
High Concentrations ◽  
The Stability ◽  
And Function ◽  
Low Ionic Strength ◽  
Affinity Interaction

Purified human erythrocyte spectrin is able to form large oligomeric species without the collaboration of any other proteins. This reversible self-assembly process is both temperature and concentration dependent and seems to be mediated by the same kinds of low affinity noncovalent associations between spectrin monomers that promote tetramer formation. Low ionic strength extracts of erythrocyte membranes also contain these oligomeric species. These results support the idea that spectrin oligomers and the factors that regulate their formation may be responsible for both the stability and the versatility of the erythrocyte membrane cytoskeleton. It is postulated that the high concentrations of spectrin necessary for oligomerization are maintained in vivo by a high-affinity interaction with ankyrin. Such a coupling of high and low affinity interactions in multifunctional proteins may have significant implications for membrane structure and function.

Stability of nucleoside triphosphate levels in the red cells of the snake

1997 ◽  
Vol 200 (7) ◽  
pp. 1125-1131
Author(s):  
R Ingermann ◽  
D Bencic ◽  
J Herman
Keyword(s):  
Atpase Activity ◽  
Red Cells ◽  
Metabolic Inhibitors ◽  
Cell Swelling ◽  
Nucleoside Triphosphate ◽  
High Ph ◽  
High Concentrations ◽  
The Stability

Nucleated red cells in the nonpregnant garter snake (Thamnophis elegans) contain relatively high concentrations of nucleoside triphosphate (NTP), largely in the form of ATP, which is found at concentrations of approximately 10 mmol l-1 relative to cell volume and 15 mmol l-1 relative to cell water. During pregnancy, levels of NTP in adult red cells rise by approximately 50 % concomitant with an increase in blood progesterone level. The stability of the NTP pool within these red cells was assessed by maintaining cells in vitro at 20 °C, without exogenous nutrients, and in the presence and absence of the metabolic inhibitors iodoacetate and/or cyanide. After 96 h, NTP levels in adult red cells not exposed to the inhibitors had decreased by only approximately 10 %, while in the presence of both inhibitors NTP levels had fallen by less than 50 %. Red cell NTP levels were not affected by acute exposure to high concentrations of progesterone either in vivo or in vitro. NTP levels were much more labile when the cells were maintained in vitro at either low or high pH. Maintenance of red cells at pH 6.0 for 24 h resulted in a decrease in NTP levels of approximately 50 % and at pH 10.0 the levels fell by approximately 80 %, while buffers containing only ATP caused no detectable degradation. Incubation at low or high pH promoted some cell swelling; however, the magnitude of the decreases in intracellular NTP concentration prompted by these pH levels could not be mimicked by incubation of red cells in hypotonic buffer. Total nonspecific ATPase activity at pH 6.0 was approximately 55 % greater than that at pH 7.4, while at pH 10.0 it was approximately 6 % of that at pH 7.4. The pH-dependent decrease in intracellular NTP levels cannot, therefore, be due to stimulation of ATPase activity, at least not at high pH. Overall, the data are consistent with the hypothesis that an appreciable portion of the NTP within these cells is compartmentalized in a stable, but pH-sensitive, pool sequestered from intracellular ATP-hydrolyzing processes.

scholarly journals The neglected part of the microbiome: Prophage TJ1 regulates the bacterial community of the metaorganism Hydra

2019 ◽  
Author(s):  
Janina Lange ◽  
Sebastian Fraune ◽  
Thomas C.G. Bosch ◽  
Tim Lachnit
Keyword(s):  
Bacterial Community ◽  
Bacterial Communities ◽  
Bacterial Colonization ◽  
Bacterial Community Composition ◽  
Broad Host Range ◽  
The Stability ◽  
And Function ◽  
Multicellular Organisms

AbstractMany multicellular organisms are closely associated with a specific bacterial community and therefore considered “metaorganisms”. Controlling the bacterial community composition is essential for the stability and function of metaorganisms, but the factors contributing to the maintenance of host specific bacterial colonization are poorly understood. Here we demonstrate that in Hydra the most dominant bacterial colonizer Curvibacter sp. is associated with an intact prophage which can be induced by different environmental stressors both in vitro and in vivo. Differences in the induction capacity of Curvibacter phage TJ1 in culture (in vitro) and on Hydra (in vivo) imply that the habitat of the prokaryotic host and/or bacterial frequency dependent factors influence phage inducibility. Moreover, we show that phage TJ1 features a broad host range against other bacterial colonizer and is directly capable to affect bacterial colonization on Hydra. From these results we conclude that prophages are hidden part of the microbiome interfering with bacteria-bacteria interactions and have the potential to influence the composition of host associated bacterial communities.

scholarly journals Characteristics of Neurokinin-3 Receptor and Its Binding Sites by Mutational Analysis

Biology ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 968
Author(s):  
Ishwar Atre ◽  
Naama Mizrahi ◽  
Berta Levavi-Sivan
Keyword(s):  
In Silico ◽  
Crucial Role ◽  
Mutational Analysis ◽  
Inhibitory Effect ◽  
Sperm Volume ◽  
Neurokinin 3 Receptor ◽  
The Stability ◽  
And Function

NKB (Neurokinin B) is already known to play a crucial role in fish reproduction, but little is known about the structure and function of NKB receptors. Based on an in silico model of the tilapia NKB receptor Tachykinin 3 receptor a (tiTac3Ra) found in the current study, we determined the key residues involved in binding to tilapia NKB and its functional homologue NKF (Neurokinin F). Despite studies in humans suggesting the crucial role of F2516.44 and M2897.43 in NKB binding, no direct peptide interaction was observed in tilapia homologs. In-silico, Ala mutations on residues F2516.44 and M2897.43 did not influence binding affinity, but significantly affected the stability of tiTac3Ra. Moreover, in vitro studies indicated them to be critical to tiNKB/tiNKF-induced receptor activity. The binding of NKB antagonists to tiTac3Ra both in-vitro and in vivo inhibits FSH (follicle stimulating hormone) and LH (luteinizing hormone) release and sperm production in mature tilapia males. Non-peptide NKB antagonist SB-222200 had a strong inhibitory effect on the Tac3Ra activation. SB-222200 also decreased LH plasma levels; two hours post intraperitoneal injection, changed sperm volume and the ratios of the different stages along the spermatogenesis in tilapia testes.

Studies on the interaction of Escherichia coli endotoxin with erythrocyte membranes

1982 ◽  
Vol 60 (7) ◽  
pp. 977-985 ◽  
Author(s):  
David V. Godin ◽  
John M. Tuchek ◽  
Maureen E. Garnett
Keyword(s):  
Escherichia Coli ◽  
Membrane Lipids ◽  
Effect Of Temperature ◽  
Erythrocyte Membranes ◽  
Simple Relationship ◽  
In Vitro Effects ◽  
The Stability ◽  
Erythrocyte Stability

Escherichia coli lipopolysaccharide (endotoxin) alters the stability of erythrocytes to hypotonic lysis although the nature and magnitude of the effect varied with temperature and with the type of red blood cell examined. Evidence has been obtained suggesting a possible modulatory role of membrane lipids in governing the molecular consequences of membrane–endotoxin interaction. The marked effect of temperature on the stabilization of red cells by endotoxin was not attributable to variations in toxin binding and was not observed with more conventional structurally unrelated antihemolytic agents. Although chemical modifications which alter the toxicity of endotoxin in vivo also modify its ability to stabilize erythrocytes in vitro, no simple relationship between in vivo endotoxin toxicity and in vitro effects on erythrocyte stability was apparent. The critical dependence of endotoxin antihemolytic effects in vitro on molecular structure may offer a convenient means of assessing the homogeneity of these preparations before performing experiments in vivo.

Lipid Metabolism as a Site of Herbicide Action

Weed Science ◽  
1973 ◽  
Vol 21 (5) ◽  
pp. 477-480 ◽  
Author(s):  
J. B. St. John ◽  
J. L. Hilton
Keyword(s):  
Membrane Lipids ◽  
Lipid Synthesis ◽  
Membrane Lipid ◽  
Cell Membrane Permeability ◽  
Glyceride Synthesis ◽  
Membrane Structure And Function ◽  
And Function ◽  
A Site

Dinoseb (2-sec-butyl-4,6-dinitrophenol) and MBR 8251 [1,1 1-trifluoro-4′-(phenylsulfonyl)-methanesulfono-o-toluidide] inhibited enzymic synthesis of glycerides in vitro. The physiological significance of this inhibition was confirmed in intact wheat [Triticum aestivumL., ‘Mediterranean’ (C.I. 5303)] seedlings; dinoseb and MBR 8251 inhibition of glyceride synthesis in vivo was evidenced by a buildup in free fatty acids and a decrease in neutral and polar lipids. Glyceride synthesis and growth were reduced approximately equally by dinoseb and MBR 8251. However, polar (membrane) lipids were reduced more drastically than growth. It is suggested that dinoseb and MBR 8251 alter membrane structure and function through an inhibition of membrane lipid synthesis. DNP (dinitrophenol) was only slightly inhibitory in either the in vitro or in vivo system. Dinoseb was more effective than MBR 8251 in destruction of cell membrane permeability of intact roots immediately after treatment.

Murine Stromal Cells Counteract the Loss of Long-Term Culture-Initiating Cell Potential Induced by Cytokines in CD34+CD38low/neg Human Bone Marrow Cells

Blood ◽  
1999 ◽  
Vol 94 (2) ◽  
pp. 529-538 ◽  
Author(s):  
Annelise Bennaceur-Griscelli ◽  
Cristina Tourino ◽  
Brigitte Izac ◽  
William Vainchenker ◽  
Laure Coulombel
Keyword(s):  
Stromal Cells ◽  
Bone Marrow Cells ◽  
Cell Potential ◽  
Self Renewal ◽  
Gm Csf ◽  
High Concentrations ◽  
And Function

Abstract Evidence has been provided recently that shows that high concentrations of cytokines can fulfill functions previously attributed to stromal cells, such as promote the survival of, and led to a net increase in human primitive progenitors initiating long-term cultures in vitro (LTC-IC) or engrafting NOD-SCID (nonobese diabetic severe-combined immunodeficient) recipients in vivo. These data prompted us to re-evaluate whether stromal cells will further alter the properties of primitive progenitor cells exposed to cytokines. Single CD34+CD38low and CD38neg cells were incubated 10 days in serum-containing or serum-free medium in the presence or in the absence of murine marrow-derived stromal cells (MS-5). Recombinant human cytokines stem cell factor (SCF), pegylated-megakaryocyte growth and differentiation factor (PEG–MGDF), FLT3-L, Interleukin (IL)-3, IL-6, and granulocyte-macrophage colony-stimulating factor (GM–CSF) were systematically added at various concentrations (10 to 300 ng/mL). Cell proliferation and LTC-IC potential were evaluated in each clone after 10 days. A striking and consistent observation was the retention of a high LTC-IC potential in clones exposed to cytokines in the presence of stromal feeders, whereas clones exposed to cytokines alone in the absence of stromal feeders rapidly lost their LTC-IC potential as they proliferated. This was reflected both by the higher proportion of wells containing LTC-IC and by the high numbers of CFC produced after 5 weeks in clones grown with MS-5 during the first 10 days. We further showed by analyzing multiple replicates of a single clone at day 10 that MS-5 cells promoted a net increase in the LTC-IC compartment through self-renewal divisions. Interestingly, these primitive LTC-IC were equally distributed among small and large clones, as counted at day 10, indicating that active proliferation and loss of LTC-IC potential could be dissociated. These observations show that, in primitive cells, stromal cells counteract differentiation events triggered by cytokines and promoted self-renewal divisions. Furthermore, the almost identical distribution of the size of the clones with or without MS-5 suggests that proliferation and function of human primitive cells may be independently regulated by external signals, and that the former is primarily under the control of cytokines.

Murine Stromal Cells Counteract the Loss of Long-Term Culture-Initiating Cell Potential Induced by Cytokines in CD34+CD38low/neg Human Bone Marrow Cells

Blood ◽  
1999 ◽  
Vol 94 (2) ◽  
pp. 529-538 ◽  
Author(s):  
Annelise Bennaceur-Griscelli ◽  
Cristina Tourino ◽  
Brigitte Izac ◽  
William Vainchenker ◽  
Laure Coulombel
Keyword(s):  
Stromal Cells ◽  
Bone Marrow Cells ◽  
Cell Potential ◽  
Self Renewal ◽  
Gm Csf ◽  
High Concentrations ◽  
And Function

Evidence has been provided recently that shows that high concentrations of cytokines can fulfill functions previously attributed to stromal cells, such as promote the survival of, and led to a net increase in human primitive progenitors initiating long-term cultures in vitro (LTC-IC) or engrafting NOD-SCID (nonobese diabetic severe-combined immunodeficient) recipients in vivo. These data prompted us to re-evaluate whether stromal cells will further alter the properties of primitive progenitor cells exposed to cytokines. Single CD34+CD38low and CD38neg cells were incubated 10 days in serum-containing or serum-free medium in the presence or in the absence of murine marrow-derived stromal cells (MS-5). Recombinant human cytokines stem cell factor (SCF), pegylated-megakaryocyte growth and differentiation factor (PEG–MGDF), FLT3-L, Interleukin (IL)-3, IL-6, and granulocyte-macrophage colony-stimulating factor (GM–CSF) were systematically added at various concentrations (10 to 300 ng/mL). Cell proliferation and LTC-IC potential were evaluated in each clone after 10 days. A striking and consistent observation was the retention of a high LTC-IC potential in clones exposed to cytokines in the presence of stromal feeders, whereas clones exposed to cytokines alone in the absence of stromal feeders rapidly lost their LTC-IC potential as they proliferated. This was reflected both by the higher proportion of wells containing LTC-IC and by the high numbers of CFC produced after 5 weeks in clones grown with MS-5 during the first 10 days. We further showed by analyzing multiple replicates of a single clone at day 10 that MS-5 cells promoted a net increase in the LTC-IC compartment through self-renewal divisions. Interestingly, these primitive LTC-IC were equally distributed among small and large clones, as counted at day 10, indicating that active proliferation and loss of LTC-IC potential could be dissociated. These observations show that, in primitive cells, stromal cells counteract differentiation events triggered by cytokines and promoted self-renewal divisions. Furthermore, the almost identical distribution of the size of the clones with or without MS-5 suggests that proliferation and function of human primitive cells may be independently regulated by external signals, and that the former is primarily under the control of cytokines.

scholarly journals Crystallizing the function of the magnetosome membrane mineralization protein Mms6

2016 ◽  
Vol 44 (3) ◽  
pp. 883-890 ◽  
Author(s):  
Sarah S. Staniland ◽  
Andrea E. Rawlings
Keyword(s):  
Self Assembly ◽  
Marked Effect ◽  
Magnetotactic Bacteria ◽  
Structure And Function ◽  
In Vitro Methods ◽  
The Subject ◽  
Key Features ◽  
And Function

The literature on the magnetosome membrane (MM) protein, magnetosome membrane specific6 (Mms6), is reviewed. Mms6 is native to magnetotactic bacteria (MTB). These bacteria take up iron from solution and biomineralize magnetite nanoparticles within organelles called magnetosomes. Mms6 is a small protein embedded on the interior of the MM and was discovered tightly associated with the formed mineral. It has been the subject of intensive research as it is seen to control the formation of particles both in vivo and in vitro. Here, we compile, review and discuss the research detailing Mms6’s activity within the cell and in a range of chemical in vitro methods where Mms6 has a marked effect on the composition, size and distribution of synthetic particles, with approximately 21 nm in size for solution precipitations and approximately 90 nm for those formed on surfaces. Furthermore, we review and discuss recent work detailing the structure and function of Mms6. From the evidence, we propose a mechanism for its function as a specific magnetite nucleation protein and summaries the key features for this action: namely, self-assembly to display a charged surface for specific iron binding, with the curvature of the surfaces determining the particle size. We suggest these may aid design of biomimetic additives for future green nanoparticle production.

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

Formation and Structure of Casein Micelles in Lactating Mammary Tissue

1970 ◽  
Vol 28 ◽  
pp. 150-151
Author(s):  
Robert J. Carroll ◽  
Marvin P. Thompson ◽  
Harold M. Farrell
Keyword(s):  
Size Distribution ◽  
G Protein ◽  
Milk Proteins ◽  
Mammary Tissue ◽  
Colloidal System ◽  
Casein Micelles ◽  
The Stability

Milk is an unusually stable colloidal system; the stability of this system is due primarily to the formation of micelles by the major milk proteins, the caseins. Numerous models for the structure of casein micelles have been proposed; these models have been formulated on the basis of in vitro studies. Synthetic casein micelles (i.e., those formed by mixing the purified αsl- and k-caseins with Ca2+ in appropriate ratios) are dissimilar to those from freshly-drawn milks in (i) size distribution, (ii) ratio of Ca/P, and (iii) solvation (g. water/g. protein). Evidently, in vivo organization of the caseins into the micellar form occurs in-a manner which is not identical to the in vitro mode of formation.

Sign in / Sign up

Export Citation Format

Share Document